<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0px;
            padding: 0px;
        }

        li {
            background-color: aqua;
            width: 100px;
            height: 20px;
            float: left;
        }

        .cl {
            clear: both;
        }

        .aaa {
            margin-top: 17px;
        }
    </style>
</head>
<body>
<div>
    <ul>
        <li>A</li>
        <li>B</li>
        <li>C</li>
        <div class="cl"></div>
    </ul>
</div>
<div class="aaa">
    <ul>
        <li>一</li>
        <li>二</li>
        <li>三</li>
    </ul>
</div>
</body>
</html>